What is polyglotism?
When you know and can use multiple languages then you are a polyglot. With a developed intellect, when you optimize your learning technique with experience you will become increasingly efficient as you go onto learn new languages.

Benefits of multilingualism
Multilingualism helps you to tap your intellectual capabilities and develops it. You start associating other things in life and approach problem solving carrying your learning to life in general. Your ears become sharper and you listen more than just hear deciding intelligently the information to keep and the one to discard.

Your grasp over your first/native language improves, you tend to construct better sentences, and your language becomes more sophisticated. You suddenly become a conversational wizard, your vocabulary shoots up and being eloquent feels second nature.